1. Field of the Invention
The present invention relates to a printed circuit board and a switch using the same. Particularly, the invention is concerned with a printed circuit board with fixed contacts of a switch formed thereof, as well as a switch using the same.
2. Description of the Related Art
A conventional printed circuit board and a switch using the same will be described below with reference to drawings.
FIG. 3 is an exploded perspective view for explaining a conventional printed circuit board and a switch using the same. This conventional switch is disposed integrally with a vehicular steering wheel for example and is used for setting a cruising speed in vehicular auto-cruising, for switching over from one such cruising speed to another, and for radio channel selection. FIG. 4 is a sectional view of a principal portion for explaining the switch shown in FIG. 3.
In FIGS. 3 and 4, a mounting member 1 is formed by molding an insulating molding material such as, for example, a glass-filled epoxy resin. The mounting member 1 has a flat plate-like support member 1a and a plurality (for example, three) of cylindrical boss portions 1b projecting outward (upward) at predetermined positions of the support member 1a. 
The boss portions 1b of the mounting member 1 are each composed of a large-diameter portion 1c and a small-diameter portion 1d, with a stepped portion being formed by the large- and small-diameter portions 1c, 1d. The boss portions 1b constitute mounting means.
A printed circuit board 2 is formed by molding an insulating molding material such as, for example, a glass-filled epoxy resin or phenolic resin and it has a flat plate-like board portion 2a, circuit patterns 2b formed in a predetermined shape on at least one side of the board portion 2a and having a predetermined electrical function, and a plurality (for example, 3+2=5) of circular mounting holes 2c and 2g formed in the board portion 2a at positions where the circuit patterns 2b are not formed.
In an inner walls 2d and 2h of the mounting holes 2c and 2g, the board portion 2a is arranged so as to exposed. For example, the mounting holes 2c and 2g are formed by blanking with use of a press.
A pair of oppositely disposed fixed patterns 2e of a switch 10 which will be described later are connected to each of the circuit patterns 2b, which patterns have a predetermined electrical function.
An elastic member 3 is formed in a generally flat plate shape by molding a transparent or translucent elastic material such as rubber and it is provided with a base portion 3a, a plurality (for example, three) of generally cylindrical retaining portions 3b for retaining upper end portions of the boss portions 1b of the mounting member 1, and boss portions 3g which are inserted through the mounting holes 2g formed in the printed circuit board 2 to mount the elastic member 3 to the printed circuit board 2. The retaining portions 3b and the boss portions 3g are formed in an outwardly projecting state from the base portion 3a. 
Movable contact portions 4, which are integral with the elastic member 3, are each formed in a generally dome shape by molding and are each provided with a generally cylindrical pressing portion 4a and a movable contact 4b (see FIG. 4) provided on the underside of the pressing portion 4a. The elastic member 3 integral with the movable contact portions 4 is disposed on the printed circuit board 2 by a suitable means so that the paired fixed contacts 2e of the printed circuit board 2 are opposed to the movable contact 4b in each movable contact portion 4. The switch 10 is formed by moving the movable contact 4b into contact with and away from the fixed contacts 2e (making ON and OFF).
The following description is now provided about a mounting process for mounting the printed circuit board and the elastic member to the mounting member.
According to this mounting process, first the mounting member 1 and the printed circuit board 2 are disposed so that the small-diameter portions 1d of the boss portions 1b on the mounting member are inserted respectively through the mounting holes 2c formed in the printed circuit board 2. As a result, the printed circuit board 2 is brought into engagement with the mounting member 1 and is positioned relative to the mounting member. Thus, the printed circuit board is made integral with the mounting member. The insertion of the small-diameter portions 1d into the mounting holes 2c is effected in a slightly tight fitting condition.
Next, in the state in which the mounting member 1 and the printed circuit board 2 are thus rendered integral with each other, the elastic member 3 is put on the printed circuit board so that the boss portions 3g of the elastic member 3 are inserted respectively through the mounting holes 2g formed in the printed circuit board and so that the small-diameter portions 1d of the mounting member 1 are respectively fitted in the retaining portions 3b of the elastic member. As a result, the paired fixed contacts 2e on the printed circuit board 2 are opposed to the movable contact 4b of each movable contact 4. In this way the mounting member 1, the printed circuit board 2 and the elastic member 3 are rendered integral with one another.
In the conventional printed circuit board 2 described above, the board portion 2a (cut-out surfaces of the printed circuit board) are exposed as they are to the mounting holes 2c formed by blanking with a press in the printed circuit board, so if the small-diameter portions 1d of the mounting member 1 are inserted into the mounting holes 2c in a slightly tight fitting condition, a powdery material 5 (see FIG. 4) formed by the blanking from the board portion 2a is scattered to one side of the printed circuit board 2. The powdery material 5 thus scattered drops onto the fixed contacts 2e (circuit patterns 2b) on the printed circuit board 2, thus giving rise to the problem that the contact between the fixed contacts 2e and the movable contact 4b both constituting a switch becomes unstable.
The problem of the powdery material 5 arises also in case of inserting the boss portions 3g of the elastic member 3 in a slightly tight fitting condition into the mounting holes 2g formed in the printed circuit board 2.
The present invention has been accomplished for solving the above-mentioned problem and it is an object of the invention to provide a printed circuit board 2 free from a fear of scattering of a powdery material from the mounting holes 2c or 2g, as well as a switch using such a printed circuit board.
In the printed circuit board according to the present invention, circuit patterns are formed on a board portion which is formed of an insulating-material, and mounting holes are formed in the board portion, the mounting holes being subjected to a through-hole plating method to form electrically conductive through-hole-plated plating layers respectively therein, further, boss portions of a mounting member formed of an insulating material are inserted respectively into the mounting holes to mount the printed circuit board to the mounting member.
In the printed circuit board according to the present invention, the electrically conductive plating layers formed respectively in the mounting holes are independent of the circuit patterns.
In the printed circuit board according to the present invention, the circuit patterns have fixed contacts of a switch.
The switch using a printed circuit board according to the present invention has the printed circuit board, a mounting member formed with boss portions, and a movable contact disposed in an opposed relation to fixed contacts, the boss portions of the mounting member being inserted respectively into mounting holes formed in the printed circuit board to mount the printed circuit board to the mounting member.
The switch using a printed circuit board according to the present invention has the printed circuit board, the printed circuit board being formed of an insulating material and provided with circuit patterns including fixed contacts of a switch and also provided with mounting through holes, and an elastic member having a movable contact disposed in an opposed relation to the fixed contacts and also having boss portions, the mounting holes formed in the printed circuit board being subjected to a through-hole plating method to form electrically conductive through-hole-plated plating layers respectively therein, the boss portions of the elastic member being inserted into the mounting holes in the printed circuit board to mount the elastic member to the printed circuit board.
In the switch according to the invention, the electrically conductive plating layers formed respectively in the mounting holes are independent of the circuit patterns.